Blenders adapted for fluid blending are known and/or utilized in a large variety of applications. In particular, such blenders for blending two or more liquid components have been suggested and/or utilized, where one component is a fragile liquid polymer material requiring special consideration in blending and mixing operations.
Liquid polymer is used, for example, in water and wastewater treatment as a flocculent and coagulant. As supplied, the polymer is suspended in oil and the polymer molecule is coiled. In this form, the polymer is ineffective, and requires activation (i.e., uncoiling) in a dilution process. However, once uncoiled, the elongated polymer molecule is fragile and susceptible to damage. While a relatively high mixing energy is required to activate the molecule in the dilution process, that same high mixing energy may damage the elongated molecule thereafter, thus impairing the effectiveness of the molecule and thus the mixture in the coagulation or flocculation process.
Passive, non-mechanical, mixers using spray nozzles or static mixers are known (see U.S. Pat. Nos. 4,664,528 and 5,426,137) for such applications. Likewise, active (mechanical) mixers utilizing impellers of various configurations are also known (see U.S. Pat. Nos. 5,338,779, 5,284,627, 5,061,456 and 5,018,871).
Mechanical mixers have the benefit of affecting variable mixing energy without reliance on water pressure to create this energy. Such designs, however, often have a high potential for damaging the polymer molecules by contact with impeller blades and the like. This drawback is heightened at low flow rates (throughput) where retention time is greater thus increasing exposure of the molecules to damaging mechanical mixing energy. Moreover, as with all mechanical systems, such blenders are more prone to mechanical failure and blender down time.
Non-mechanical mixers typically rely on high water pressure to produce mixing energy. Thus, such systems lose mixing energy as the flow rate decreases. Moreover, such systems can control mixing energy only when water pressure control is available.
Further improvement in such fluid blending apparatus and methods, directed to improving reliability and effectiveness thereof under a variety of conditions, could thus still be utilized.